A headphone has been used as a device through which sound output from an audio reproduction device is heard. A typical headphone includes a headband provided in contact with the head of a user, and housings provided on the left and right ends of the headband. Each of the housings accommodates an audio output means constituted by a speaker or the like. There are known a considerable number of types and folding systems of a headphone (Patent Document 1, Patent Document 2). A known foldable headphone often includes two or three, or more folding rotational shafts disposed on each of an L side and an R side.